During The Hundred Years War, a detachment of soldiers return home to the estate of Lady Matilda (Lena Headey), second wife of Sir Walter de Mellerby, who has been captured by the French. Years of war and bad crops have driven the estate into debt to the church and Matilda is unable to pay the ransom for his release, but fortunately the soldiers have captured Jacques de Saint Amant, son of the man holding her husband, who can be exchanged for her husband along with a ransom large enough to settle her debts.
Matilda goes to see the bishop (Ian McNeice) to ask for an extension in the payment date. The bishop grants her ten more days, but if she fails to pay, she must have sex with him "in forty-seven different ways".
All she has to do is keep Jacques alive until the deadline, which is not an easy task when people start dying of a mysterious plague and evidence begins to pile up that Jacques is more than he appears.
This movie has the following tropes:
- Carved Mark: Anazapta is the word carved in the back of Nicholas when he's found dead of the plague.
- CPR: Clean, Pretty, Reliable: Matilda accidentally invents CPR several centuries early when the villagers dunk Jacques in the well. She orders him fetched out, but he's already drowned. An old man advises her to breathe life into him, but no-one else is willing to touch him so she does it herself, first blowing air on his face, then directly into his mouth. When this doesn't work, she pounds on his chest in frustration, and the combination of the two manages to revive him. Giving Jacques the Kiss of Life fuels rumours that there's something more going on between them.
- A Date with Rosie Palms
- Matilda slips a hand under her chastity belt while thinking of her handsome French hostage. Though the corpse falling through the canopy of her four-poster bed is something of a Moment Killer.
- When Matilda agrees to the Scarpia Ultimatum, the bishop asks for a "down payment" to seal the deal. Matilda retorts, "You have a hand. Use it!" and storms out. Later when Matilda needs another favour he insists on his down payment. Cut to Matilda furiously scrubbing her hands.
- Dramatic Irony: Unknown to Matilda, her husband has escaped from the French and is slowly making his way back home over the course of the movie.
- Every Scar Has a Story
- Jacques has a cross-shaped scar on his chest. It's the Mark of Shame branded on the Child by Rape of Joan de Mellerby.
- Jacques' jailor Randall Bacon wears a patch to cover his severed nose. It was cut off in punishment for sheltering Joan de Mellerby after she was raped and left for dead in the forest.
- Fainting: Matilda faints when told her husband hasn't returned from the war, thinking he's dead. It's only after she regains consciousness that she's told that he's actually been captured by the French.
- Going Commando: Used for a humorous bait-and-switch when Matilda needs the bishop to hold mass for the village after their priest dies. When the bishop wants to know what he's getting in exchange she lifts her skirt. Given the medieval era the audience assumes she's not wearing underwear and is flashing him, but the bishop's exasperated reaction makes it clear that she is wearing a chastity belt, and he's going to need her cooperation if he wants to get it off.
- It Was Here, I Swear!: Halfway through the movie, the priest receives a letter from Jacques' father revealing his son was killed in battle. After Jacques reveals his true identity, he plays on the priest's guilt to get him to hand over the letter. The priest commits suicide soon after and when Bacon—who overheard their conversation—tries to warn Matilda their hostage is an imposter, she only finds a letter agreeing to her ransom on the condition that Jacques is well treated, and has her manservant flogged and thrown into a cell for his supposed bungle.
- Gainax Ending: When Sir Walter finally returns to the village and confronts Jacques, he reveals that he can't be the son of Joan because he killed the baby and ate its heart in his madness. After Walter is killed, Jacques declares his revenge over and staggers off into the countryside, until he finally comes across another village and a woman who recognises him as "William." The End.
- Impoverished Patrician: The estate has been bankrupted by rains ruining the crops and the Forever War being waged in France. When Matilda has to go see the bishop, she protests that she has nothing to wear as her husband has pawned all her fine clothes. She shocks the priest by dressing in the finery of Sir Walter's previous wife, which he refused to sell.
- Kiss of Death: Jacques 'forgives' the priest and the physician with a kiss, but both men die soon afterwards.
- Laser-Guided Karma: Randall Bacon and Lady Matilda are the only two people to survive Jacques Roaring Rampage of Revenge.
- Maybe Magic, Maybe Mundane: It's left ambiguous whether Jacques is driving men to their deaths via sorcery or poison or just playing on their guilt.
- A Match Made in Stockholm: Matilda has a husband who's spent years fighting in far-away wars (and it's implied Sir Walter neglects her even when he's home), so the way she keeps having to save Jacques' life fuels plenty of rumours about what might be going on with her handsome French captive. Jacques in turn makes no secret of his attraction to her, though she resists his charms until after she discovers what a ratbag her husband was.
- Never Trust a Trailer: The American release changed the name to Black Plague and the trailer made it look like Lady Matilda is trying to rally her village in the face of the plague. In truth it's a mystery thriller set as the Black Death is first starting to infiltrate Britain.
- Oral Fixation: The bishop's minion Peacock is constantly blowing on a short flute (to his master's annoyance). When he's startled in the midst of an attempted murder, he accidentally swallows it and runs off tooting.
- Plagued by Nightmares: Jacques is tormented by visions of what happened to Joan and the upcoming plague.
- Scarpia Ultimatum: Matilda is in debt to the bishop, but she asks for an extension of ten days to give time for the ransom to arrive. The bishop agrees on condition that if she fails to pay the debt, she'll have to "humour an old man in forty-seven different ways", and even shows her erotic parchments depicting some of those ways to make it absolutely clear what he's talking about. It's soon revealed that he's behind several attempts on Jacques life so he can claim both Matilda and her estate for himself.
- Self-Harm: Jacques is shown carving his knife into the scar on his chest until it bleeds. This foreshadows The Reveal that he's not actually Joan's child, but may be another man possessed by her spirit and driven to carry out revenge on her behalf.
- Tampering with Food and Drink: Jacques poisons the communion wine, killing the inhabitants of the village when they take mass.
- Town with a Dark Secret: At first it looks like Matilda is living in the shadow of her husband's love for his previous wife Joan. It turns out Joan was having an affair and revealed this during confession. The priest broke the seal of the confessional to curry favour with Sir Walter, who hanged Joan's lover, denounced her as a whore and offered a shilling to every man of the village who wanted to rape her.
- Vow of Celibacy: Matilda is wearing a chastity belt and her husband holds the key. Though it doesn't stop her masturbating and when she sleeps with Jacques he just cuts the straps.
- With Friends Like These...: Matilda regards her advisors as her friends and is distraught over their deaths, but all of them are withholding secrets from her.
- Who Are You?: Jacques gets asked this whenever someone sees his scar.
- Would Hurt a Child: The movie opens with Sir Walter with his sword poised over a squalling baby with a cross branded on his chest. For much of the movie it looks like he hadn't gone through with killing the baby, only for Sir Walter to reveal that he killed the child, then tore out its heart and ate it so Jacques can't possibly be him.